1. Field of the Invention
Embodiments of the present invention relate to a fuel cell system and a method of control of the same.
2. Related Art
A fuel cell system is known in the art, which is provided with a fuel cell stack configured to generate electric power by an electrochemical reaction between hydrogen gas and air, a radiator configured to lower a temperature of a cooling water for the fuel cell stack. The fuel cell system is further provided with a cooling water feed passage connecting together an outlet of an in-radiator cooling water passage in the radiator and an inlet of an in-stack cooling water passage in the fuel cell stack. The cooling water feed passage includes a feed side branching point, a radiator outflow passage from the outlet of the in-radiator cooling water passage to the feed side branching point, and a stack inflow passage from the feed side branching point to the inlet of the in-stack cooling water passage. The fuel cell system is further provided with a cooling water discharge passage connecting together an outlet of the in-stack cooling water passage and an inlet of the in-radiator cooling water passage. The cooling water discharge passage includes a discharge side branching point, a stack outflow passage from the outlet of the in-stack cooling water passage to the discharge side branching point, and a radiator inflow passage from the discharge side branching point to the inlet of the in-radiator cooling water passage. The fuel cell system is further provided with a bypass cooling water passage connecting together the feed side branching point and the discharge side branching point, a check valve arranged in the bypass cooling water passage and enabling the cooling water to flow through the bypass cooling water passage only from the cooling water discharge passage to the cooling water feed passage, a stack side cooling water pump arranged in the stack inflow passage so that its outlet faces the fuel cell stack, and a radiator side cooling water pump arranged in the radiator inflow passage so that its outlet faces the radiator. In the fuel cell system, if a temperature of the cooling water flowing out from the in-stack cooling water passage is lower than a prescribed temperature, the fuel cell system drives the stack side cooling water pump and stops the radiator side cooling water pump, whereby the cooling water circulates through a first route formed by the stack inflow passage, in-stack cooling water passage, stack outflow passage, and bypass cooling water passage, without flowing through the in-radiator cooling water passage. If the temperature of the cooling water flowing out from the in-stack cooling water passage is higher than the prescribed temperature, the fuel cell system drives the stack side cooling water pump and the radiator side cooling water pump, whereby the cooling water circulates through a second route formed by the cooling water feed passage, in-stack cooling water passage, cooling water discharge passage, and in-radiator cooling water passage, without flowing through the bypass cooling water passage (for example, see Japanese Patent Publication No. 2010-097709A). According to Japanese Patent Publication No. 2010-097709A, the radiator side cooling water pump which is stopped acts as a closed valve. For this reason, the cooling water having flowed through the stack outflow passage flows into the bypass cooling water passage without flowing into the radiator inflow passage, therefore the cooling water circulates through the first route. That is, if the temperature of the cooling water is low, the cooling water is kept from being cooled by the radiator.